Although they are not (at present) ultralight, I really like the concepts behind these wonderful lamps. Lumir-k: Cooking oil fueled LED lamp: & Lumir-C Candle Powered Led lamp:
Lumir C:
Lumir K:
This is a similar concept, power from heat: https://drop.com/buy/biolite-campstove-bundle#overview & this: https://www.theultralighthiker.com/2015/07/20/power-from-heat/
PS: You should be able to make this system work with a Peltier on a chimney as in: https://www.theultralighthiker.com/2019/05/29/tim-tinker/
